His fellow Democrats are eager to avoid the subject of Menendez's bribery trial, hoping that he is exonerated and then he can focus on his 2018 reelection battle in the Garden State.

But there is fear inside Democratic circles that Menendez may get convicted and refuse to give up his seat, facing pressure to resign or an expulsion vote in the Senate. If the Democrat were to step aside while Gov. Chris Christie remains office, the Republican would pick a replacement.

Yet if Menendez's legal problems worsen and he decides to run for reelection, it could jeopardize a key seat in a critical election year.

Senate Minority Leader Chuck Schumer on Wednesday declined to say if he would stand by Menendez if he's convicted. Instead, Schumer said simply that the New Jersey politician is putting up a "spirited defense" and deserves to be presumed innocent until proven guilty.

"Sen. Menendez is issuing a spirited defense," Schumer said Wednesday. "We all believe in the presumption of innocence in this country, and Sen. Menendez is fighting very hard. And we respect that greatly."

Asked if he would continue to stand by Menendez if the New Jersey Democrat were convicted, Schumer ignored the question.

Democrats who face reelection in 2018 also are in an awkward position -- especially as prosecutors lay out the charges in a trial that could take weeks.

"We are a country of laws," said Sen. Joe Manchin, a Democrat from the red state of West Virginia, who faces reelection next year. "And I think people should just let this process go through before they come to judgment in any way shape or form."

Asked if he'd continue to stand by Menendez if he were convicted, Manchin declined to say, adding: "Whatever the verdict is we'll deal with it at that time."

Sen. Jon Tester, the Montana Democrat who also faces voters next year, also declined to comment, saying his attention has been focused on wildfires in his state.

"I haven't really been paying attention to the trial," Tester said.

Menendez is currently on trial for public corruption two years after charges were filed against the New Jersey politician and his alleged co-conspirator, Dr. Salomon Melgen.

Prosecutors say Menendez acted in his "official capacity" to help advance personal and business interests of Melgen, and call the men's relationship a "corrupt pact."

Prosecutors accuse Menendez of accepting gifts from Melgen, including luxurious vacations and large campaign donations, in exchange for help in government matters, including disputes over Medicare reimbursements.

However, Menendez has denied the accusations and says he and Melgen are old friends, arguing that the gifts are legal.

"I have committed my entire adult life since I was 19 to fighting for the people of New Jersey," Menendez said Wednesday morning before entering federal court. "Never, not once, not once have I dishonored my public office."

Menendez also requested to modify the trial so he could be present for "critical votes," but his request was rejected by the federal judge overseeing the trial.

Menendez addressed the possibility of missing those votes while speaking to the press on Wednesday.

"Now the Constitution, like any citizen, gives me the right to ultimately assist in my defense in court and I intend to be here every day. The Constitution also gives me the right to cast a vote on behalf of the people I represent in the United States Senate. When the conflict exists if it becomes a conflict, a clash between those constitutional rights, I will make a decision based upon the gravity of the situation and the difference that my vote could make," he said.

Sixty-seven members must vote to expel a senator from the body, meaning at least 15 Democrats would have to join the 52-member Senate Republican Conference in doing so.

The governor is responsible for picking a possible replacement if he's convicted. If he is forced out of the Senate, depending on the timing, it could fall on current Gov. Chris Christie or his successor -- New Jersey has a governor's race this year and Christie's term is up in January.